When is a desmoid not a desmoid? Endometrial cancer as an extracolonic manifestation of MYH Associated Polyposis (MAP)

Case history A 68 year old Caucasian woman presented with a lump in her right groin and lower abdominal pain. No changes in bowel habit or other bowel symptoms were reported. Previous medical history included endometrial cancer diagnosed at age 57, treated by hysterectomy and bilateral salpingo-oophorectomy. The family history was negative for desmoids, colon polyps and cancer. By CT scan, a 4 x 3 cm soft tissue mass arising from the right rectus muscle and tethered to bowel loops was identified. It was felt to represent a desmoid. Before resecting this mass, due to bowel tethering, a colonoscopy was performed. The cecum was completely replaced by a carpeting villous adenoma. Two tubular adenomas and one tubulovillous adenoma, all with lowgrade dysplasia, were noted. During definitive surgery, the lesion arising from the sigmoid mesentery and suspected to be a desmoid, was shown to be a well-differentiated adenocarcinoma with endometrioid features. 28 tubulovillous adenomas and hyperplastic polyps, with no malignancy or dysplasia were identified in the subtotal colectomy. The clinical impression was that of attenuated polyposis and metastatic endometrial carcinoma. Results APC gene testing was negative. This patient was homozygous for the common c.536A>G mutation in MYH.